The original objective of developing methods to recognize allergy-proneness at the earliest feasible age is unchanged. There will be continued careful follow-up of high-risk children already in the study to more accurately delineate the incidence and persistence of symptoms of allergy and their relationship to immunochemical changes identifiable in the newborn period. In each instance determinations will be made of all five immunoglobulin levels in amniotic fluid, cord blood, maternal blood and in serial specimens of serum obtained during infancy. Specific IgE, IgG and IgD antibodies to commonly encountered antigens will be studied. Viral isolation will be sought at times of fever or upper respiratory infection and an assessment of the effect viral illnesses have on immunoglobulin levels, class specific antibodies and on the appearance of allergic symptoms will be made. Preliminary data indicates that striking reciprocal changes occur over a period of time involving serum IgE and IgD antibodies. A study will be made to learn the possible prognostic implications of immunoglobulin and antibody pattern changes during normal maturation, following routine immunizations, after the institution of pasteurized cow's milk feedings and during illness and convalescence from viral infections. A lymphocyte culture model will be used to test selected hypotheses. Total serum and amniotic fluid IgG and IgA will be determined by radial immuno-diffusion. Total IgE and IgD as well as specific antibodies of these classes will be determined by solid phase paper disc radioimmunoasssys. Antibodies of the IgG class will be measured by double antibody radioimmunoassay. Specific IgE and IgD antibodies will be isolated by immunoadsorption and affinity chromatography.